lkml.org 
[lkml]   [2018]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH 04/13] x86/pkeys/selftests: Avoid printf-in-signal deadlocks
From
Date

From: Dave Hansen <dave.hansen@linux.intel.com>

printf() and friends are unusable in signal handlers. They deadlock.
The pkey selftest does not do any normal printing in signal handlers,
only extra debugging. So, just print the format string so we get
*some* output when debugging.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
---

b/tools/testing/selftests/x86/pkey-helpers.h | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff -puN tools/testing/selftests/x86/pkey-helpers.h~pkeys-selftests-avoid-print-in-signal-deadlocks tools/testing/selftests/x86/pkey-helpers.h
--- a/tools/testing/selftests/x86/pkey-helpers.h~pkeys-selftests-avoid-print-in-signal-deadlocks 2018-05-09 09:20:19.738698404 -0700
+++ b/tools/testing/selftests/x86/pkey-helpers.h 2018-05-09 09:20:19.742698404 -0700
@@ -26,30 +26,26 @@ static inline void sigsafe_printf(const
{
va_list ap;

- va_start(ap, format);
if (!dprint_in_signal) {
+ va_start(ap, format);
vprintf(format, ap);
+ va_end(ap);
} else {
int ret;
- int len = vsnprintf(dprint_in_signal_buffer,
- DPRINT_IN_SIGNAL_BUF_SIZE,
- format, ap);
/*
- * len is amount that would have been printed,
- * but actual write is truncated at BUF_SIZE.
+ * No printf() functions are signal-safe.
+ * They deadlock easily. Write the format
+ * string to get some output, even if
+ * incomplete.
*/
- if (len > DPRINT_IN_SIGNAL_BUF_SIZE)
- len = DPRINT_IN_SIGNAL_BUF_SIZE;
- ret = write(1, dprint_in_signal_buffer, len);
+ ret = write(1, format, strlen(format));
if (ret < 0)
- abort();
+ exit(1);
}
- va_end(ap);
}
#define dprintf_level(level, args...) do { \
if (level <= DEBUG_LEVEL) \
sigsafe_printf(args); \
- fflush(NULL); \
} while (0)
#define dprintf0(args...) dprintf_level(0, args)
#define dprintf1(args...) dprintf_level(1, args)
_
\
 
 \ /
  Last update: 2018-05-09 19:19    [W:0.122 / U:0.704 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site